Method and device for determining parameters for spectacle fitting

ABSTRACT

A depth information detection device detects an item of depth information relating to a user&#39;s head, including a distance from the user&#39;s head to the device. On the basis of this depth information and, if applicable, additional information such as images, an evaluation device determines the desired parameters for fitting the spectacles, such as centering parameters.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of internationalapplication PCT/EP2017/057880, filed Apr. 3, 2017, and designating theUnited States, which claims priority to German patent application DE 102016 106 121.2, filed on Apr. 4, 2016, both of which are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

The present application relates to methods and devices for determiningparameters for fitting spectacles to a person's head, in particular thedetermination of centration parameters. Centration parameters of thistype are used to correctly arrange, that is to say center, spectaclelenses in a spectacle frame, such that the spectacle lenses are worn ina correct position relative to the person's eyes.

BACKGROUND

A device of the generic type and a method of the generic type are knownfrom U.S. Pat. No. 7,740,355 B2, for example.

The procedure used in the document involves using a pair of imagerecording units to generate stereo image data of a person's head orparts of the head. A three-dimensional model of the head is thencalculated from the stereo image data. Desired optical parameters can bedetermined on the basis of the three-dimensional model. A correspondingmethod is likewise described. Instead of the pair of image recordingunits, a pattern projection can also be used in a variant described asan alternative in the document.

In the case of the device in U.S. Pat. No. 7,740,355 B2, the person tobe examined is positioned in front of the device, and the imagerecording units then record corresponding images of the head or partsthereof. In this case, inaccuracies may occur in relation to thepositioning of the person, that is to say that the person may bepositioned in a manner deviating from a desired setpoint position, inparticular a desired setpoint distance. This may make it more difficultto determine accurate dimensions from the images recorded by the imagerecording units, which are required for the determination of theparameters. Moreover, the procedure in U.S. Pat. No. 7,740,355 B2necessitates finding corresponding points or image regions in imagepairs recorded by the pair of image recording units. Depending onlighting conditions it may be difficult to implement this for asufficient number of image points.

US 2015/323310 A1 discloses methods and devices in which a pupillarydistance and a scale are determined by using a distance measurement. Thedocument does not deal with determining parameters for spectaclefitting.

US 2018/0042477 A1, published subsequently, discloses a method and acorresponding device for determining parameters for spectacle fitting inwhich a measuring unit is used to detect items of depth information inrelation to a user's head, wherein the measuring unit determines thedistance between at least one eye and an image recording unit of themeasuring unit. A parameter of the use position of spectacles or of aspectacle frame is then determined taking account of the distancedetermined.

US 2010/0220285 A1 discloses a method for determining parameters forspectacle fitting, in particular a pupillary distance, in which adistance between a device used and a patient is measured and thepupillary distance is measured on the basis of the distance by means ofscaling.

U.S. Pat. No. 5,818,954 discloses specularly reflecting an illuminationonto an optical axis of a camera.

A light field camera is disclosed in DE 10 2014 108 353 A1.

SUMMARY

It is therefore an object of the present disclosure to provide methodsand devices in which an accuracy of the determination of parameters forspectacle fitting, in particular in the case of inaccurate positioningof a person to be examined as mentioned above, is improved.

Methods and devices for the determination of parameters for spectaclefitting are provided for this purpose.

In accordance with a first and second aspect, a method for determiningparameters for spectacle fitting is provided, which comprises: detectingdepth information in relation to a user's head, the depth informationcomprising a distance between the user's head and a device used for thedetecting, and determining parameters for spectacle fitting on the basisof the depth information.

The depth information can also comprise a plurality of distances betweenthe head and the device at different locations of the head, which aredetected at the same time or at different times.

Moreover, in the case of the first aspect, a 2D image (also referred tohereinafter simply as image) of the head is recorded, wherein recordingthe 2D image and detecting the depth information are carried out via acommon optical axis.

In the context of the present application, spectacle fitting isunderstood generally to mean fitting spectacles to a specific person, inparticular to the person's head. Such spectacle fitting can begin forexample with the selection of a specific type of spectacle frame, inparticular a specific spectacle frame product. An expert such as anoptician generally checks whether the spectacle frame fits the person'sanatomy (e.g., in relation to size of the frame, width of the nosepiece,earpiece length). The frame fit is then checked (e.g., adaptation ofnose pads, adaptation of the earpieces to the geometry of the face).Finally, various parameters are measured, e.g., pupillary distance,corneal vertex distance, forward inclination of the frame, frame diskangle, fitting height. This measurement of the various parametersmentioned above is referred to as centration measurement or spectaclelens centration. Some of the measured parameters influence the spectaclelens power, e.g., the corneal vertex distance. Other parametersdetermine how the spectacle lenses must be positioned in the frame orhow they must be incorporated into the frame, e.g., the distance betweenthe centers of the pupils when “looking to infinity” (pupillarydistance) or the fitting height. Still other parameters can be used tocalculate and manufacture spectacle lenses in a manner particularly wellcompatible and individual to the person, e.g., the forward inclinationof the frame and the frame disk angle.

In the context of the present disclosure, parameters for spectaclefitting should generally be understood to mean indications which arerequired or usable for the spectacle fitting described above. Theseinclude, for example, dimensions relating to the person's head, inparticular relating to the eye portion, a type of spectacle frame anddimensions of the spectacle frame and also the spectacle frame fit onthe face.

The parameters for spectacle fitting may be, in particular, centrationparameters which can be used for the spectacle lens centration explainedabove and which describe e.g., anatomical features of the user (e.g.,distance between the pupils of the eyes) and a position of spectacles onthe head. Examples of such centration parameters are described in DINISO 13666, edition of 2013-10, namely for example monocular pupillarydistance or pupillary distance. In this case, the monocular pupillarydistance is the distance between the center point of the pupil and thecenter line of the person's nose or the bridge of the spectacle framefor the case where the eye is in the primary position. The primaryposition corresponds to the position of the eyes with straight head andbody posture and gaze directed straight ahead. The parameters forspectacle fitting can also comprise dimensions of a spectacle frame. Theparameters for spectacle fitting can be determined on the basis of areal spectacle frame worn by the person, or else on the basis of avirtual spectacle frame that is fitted to a model of a head that iscreated on the basis of the depth information. In this case of using avirtual spectacle frame, the parameters for spectacle fitting can alsocomprise a type of a selected spectacle frame or parameters describingthe selected spectacle frame, e.g., dimensions thereof.

By determining a distance between the depth information detection unitand the head of the person to be examined, it is possible to compensatefor inaccurate positionings of the person to be examined, i.e.,positionings that deviate from a desired setpoint position, during thedetermination of the parameters for spectacle fitting.

The method can further comprise determining a current head position(actual head position), in particular on the basis of the depthinformation, e.g., compared with a setpoint head position. In this case,the head position can comprise the position of the head in space andalso the orientation thereof (e.g., inclination, viewing direction). Inthis case, the head position can comprise for example a lateral headrotation (i.e., about the person's body axis), a head position in anaxial direction (relative to the measuring device), a lateral headinclination (i.e., in the direction of a shoulder) or a head inclinationalong the body axis (i.e., toward the front or toward the back), whereinthe head position can be determined relative to the device according tothe disclosure, e.g., to the depth information detection unit. Headpositions relative to the device according to the disclosure arerelevant for example for the correct arrangement of the person in frontof the device according to the disclosure (e.g., within the measurementvolume). The head inclination (along the body axis) has a greatinfluence on the measurement of the fitting height. Taking it intoconsideration is therefore relevant to spectacle lens centration and canbe used, if appropriate, for the subsequent correction of the fittingheight. Determining the parameters for spectacle fitting is carried outon the basis of the determined actual head position. In this way, it ispossible to take into account e.g., deviations from the setpoint headposition and/or head position (e.g., in an axial direction) relative toa device used during the determination of the parameters for spectaclefitting. In this case, as already described above, the actual headposition can comprise a lateral inclination of the head or aninclination of the head toward the front or back. This is particularlyrelevant if the intention is to take account of the natural, habitualhead posture of the person at the time of determining the parameters forspectacle fitting, since the inclination of the head can influence thedetermination of some parameters for spectacle fitting, e.g., thedetermination of a frame forward inclination or the determination of afitting height. For this purpose, the person may be requested to adoptthe natural head posture, which is then detected as the actual headposition. This detected actual head position is then used fordetermining the parameters for spectacle fitting. In this regard, theparameters for spectacle fitting can be determined appropriately for thenatural head position.

By way of example, for this purpose, from the depth information it ispossible to create at least one coarse 3D model of the head, from whichthe user's head posture and head position can be seen. As a result, theuser can be given feedback in relation to the positioning of the head;by way of example, the user can be instructed to position the headdifferently for a measurement, for example if relevant parts of the headcannot be detected. Moreover, it is also possible to ascertain if thehead posture differs from a previously ascertained habitual head postureof the user or if a zero viewing direction or main viewing directionthat is desired for a measurement is not present. Consequently, theuser's head can be positioned as optimally as possible in themeasurement region of the device.

Determining the parameters for spectacle fitting can then be carried outon the basis of the recorded image of the head. During the recording ofthe image, the person can wear a spectacle frame without spectaclelenses or with support disks (simple plastic disks with no opticalpower), or spectacles with spectacle lenses (lenses having opticalcorrective power), or else no spectacle frame. Support disks of thistype are for example sometimes incorporated in new spectacle frames atan optician's store. In the last case, the method can then measure thethree-dimensional topography of the face and determine anatomicalparameters (e.g., the distance between the pupils) as the parameterswhich can then be used for spectacle fitting. By using thethree-dimensional topography, parameters of this type can be determinedin particular independently of the head position.

The recording of the image makes it possible to use further items ofinformation in addition to the depth information for determining theparameters for spectacle fitting, for example dimensions of the person'shead that are taken from the image.

In this case, the method can comprise scaling the recorded image on thebasis of the depth information and/or scaling parameters for spectaclefitting, the parameters having been determined on the basis of theimage, on the basis of the depth information. Scaling the recorded imageon the basis of the depth information makes it possible to achieve amore accurate determination of the parameters for spectacle fittingsince in this way the recorded image can correctly reproduce dimensionsand these dimensions can be taken from the image.

The method can further comprise rectifying the recorded image on thebasis of the depth information. In this case, rectifying should beunderstood as aligning and/or correcting the recorded image, such thate.g., even in the case of an oblique head position leading todistortions in the image, correct parameters for spectacle fitting aretaken from the rectified image.

Detecting the depth information and/or recording an image can berepeated a number of times, wherein the method further comprises acombination of the respective generated items of depth informationand/or images, e.g., by an averaging over time. A method suitable forthis is described for example in “Rapid Avatar Capture and Simulationusing Commodity Depth Sensors”; A. Shapiro, A. Feng, R. Wang, Hao Li, M.Bolas, G. Medioni, E. Suma in Computer Animation and Virtual Worlds2014, Proceedings of the 27th Conference on Computer Animation andSocial Agents, 05/2014-CASA 2014.

Such averaging makes it possible to increase the accuracy of thedetermination of the parameters for spectacle fitting. However, aplurality of items of depth information and/or a plurality of images canalso be combined differently than by averaging to increase the accuracy.By way of example, this combining can be implemented by temporal fittingof a function (or of a plurality of functions; referred to in English as“fit”), e.g., fitting of a polynomial function or other suitablefunctions, or else combined spatial and temporal fitting of thefunction, e.g., of polynomial and spline functions. A fit is implementedby way of a plurality of temporally successively recorded items of depthinformation or images in the case of temporal fitting of the functionand in addition spatially by way of the images or the depth information(e.g., across different parts of the detected face) in the case ofcombined spatial and temporal fitting. In this case, one or a pluralityof corresponding functions are fitted to the items of depth informationand/or images, e.g., by fitting of coefficients of the function (e.g.,polynomial coefficients in the case of a polynomial function), such thatthe function is as close as possible to the items of depth informationand/or images. Further processing steps can then be carried out on thebasis of the function or the functions.

Combining the images or items of depth information, e.g., by averagingor fitting of a function, can be done using a rigid registration method(i.e., a method which uses only rotations and translations) to bringdifferent items of depth information and/or recorded images tocongruence. In this case, parts, e.g., measurement data, of the depthinformation that relate to the same part of the head or parts of theimages that relate to the same part of the head are brought tocongruence. This is necessary particularly if the head moves between theindividual measurements. However, non-rigid methods (i.e., methods whichalso use other operations such as distortions) can also be used entirelyor for some parts of the items of depth information and/or images, e.g.,to take account of movements such as eyelid movements, for example thedynamic fusion method (described for example in “DynamicFusion:Reconstruction and tracking of non-rigid scenes in real-time”, RichardA. Newcombe, Dieter Fox, Steven M. Seitz; The IEEE Conference onComputer Vision and Pattern Recognition (CVPR), 2015, pp. 343-352).

According to an aspect of the invention, non-rigid methods of this typeare used only for regions of the face which either are not relevant tothe later determination of parameters or can move rapidly. The two typesof registration methods mentioned above for bringing the differentmeasurements (depth information and/or images) to congruence can becarried out independently of one another or in combination.

In this case, the method can further comprise rejecting images and/oritems of depth information which satisfy predetermined criteria. Thecriteria can comprise for example a presence of a head posture that isunsuitable for the measurement, e.g., in such a way that parts ofinterest such as eyes are not visible, or a presence of a closed eyelid.As a result, images and/or items of depth information that are lesssuitable for determining the parameters for spectacle fitting (e.g.,images in which an eyelid is closed) can be rejected.

The method of the first aspect can further comprise, and the method ofthe second aspect further comprises: representing a model of the head onthe basis of the depth information, and virtually fitting spectacles tothe model, wherein the parameters for spectacle fitting are determinedon the basis of the virtual fitting. In such a case, it is typical forthe person not to wear spectacles during the detection of the depthinformation and, if appropriate, the images, such that a model of thehead without spectacles can be created more easily. Various spectacleframes can then be fitted to this model virtually, i.e., likewise asmodels e.g., on a display. From the virtual fitting it is then possibleto determine the parameters for spectacle fitting, e.g., a type of thespectacles then to be used in reality, dimensions of the spectacles thento be used in reality and/or centration parameters therefor.

It is thus possible here for the detected depth information, ifappropriate together with recorded images, also to be displayed as a 3Dmodel of the head on a display. In other words, in this case, a 3D modelof the head can be displayed in real time given an appropriaterepetition rate of the depth information detection unit, whichcorresponds to a virtual mirror. This 3D model can then be combined withvarious virtual spectacle frames to give the person a first impressionof the visual effect of various spectacle frames. One of the spectacleframes can then be selected. The type of this spectacle frame canlikewise be regarded as a parameter for spectacle fitting. Moreover, itis possible, during such fitting of a virtual spectacle frame, todetermine parameters for spectacle fitting which are then used forfitting real spectacles and which describe dimensions of the spectacleframe. This can be done for example by varying such parameters until anoptimum fit is attained. Examples of such parameters are e.g., diskwidth, disk height and bridge width of the spectacle frame. In thisregard, by way of example, the bridge of spectacles can be fitted to theshape of the bridge of the nose in the 3D model.

Centration parameters can then likewise be determined on such a selectedvirtual spectacle frame on the 3D model of the head. In other words,with exemplary embodiments of the present disclosure it is possible toimplement centration parameters with real spectacle frames (which areworn by the person during the measurements) or else with virtualspectacle frames (which are fitted to a 3D model of the head).

In addition, provision is made of a computer program having a programcode which, when executed on a processor, has the effect that theprocessor carries out one of the methods described above and/or controlsthe carrying out thereof. The computer program can be stored on acomputer-readable medium.

In accordance with a third aspect, a device for determining parametersfor spectacle fitting is provided, comprising a depth informationdetection unit for detecting depth information with respect to a user'shead, the depth information comprising at least one distance between thehead and the device, and an evaluation unit configured to determineparameters for spectacle fitting on the basis of the detected depthinformation.

By determining a distance between the depth information detection unitand the head of the person to be examined, it is possible to compensatefor positionings of the person to be examined that deviate from asetpoint position or typical position, during the determination of theparameters for spectacle fitting.

The depth information detection unit can comprise a light field camera.A light field camera of this type is also referred to as a plenopticcamera.

In a manner similar in a way to holographic recording systems, lightfield cameras capture the so-called light field of a scene. Thisinvolves recording not just intensity information, as in the case of aconventional camera, but rather additional information about thedirection from which a respective light ray emanates. As a result, inthe case of a light field camera, the recorded signal (which is recordedfor example with a conventional image sensor) contains both imageinformation and depth information, which are obtained from the intensityinformation and the information about the direction of the light rays.As a result, a recorded object such as, for example, the person's headcan be reconstructed three-dimensionally at least to a certain degree(depending on the implementation of the light field camera), anddistances between the head and the light field camera are detected. Withsuch a light field camera it is thus possible for example to combine thefunctionality of the depth information detection unit and thefunctionality of a camera. A correspondingly compact construction ispossible as a result.

Some embodiments of such light field cameras make use of amulti-microlens array mounted in a defined plane upstream of an imagesensor. The individual lenses of the microlens array generate differentitems of image information on the image sensor. The light field can bereconstructed from the entire image information on the image sensor.

The depth information detection unit can be configured to detect a depthprofile of a region of interest of the head. Depth profile is understoodto mean an indication of a distance between points of the region ofinterest and a reference surface (defined e.g., by the depth informationdetection unit) depending on a position in a plane parallel to thereference surface, for example a position in a recorded 2D image. On thebasis of the depth profile, the evaluation unit can display a model ofthe region of interest as it were as a virtual mirror, which can enablee.g., virtual fitting of spectacles. In this case, it should be takeninto consideration that, at the time when the depth information andimage information are generated, the user can either wear a spectacleframe or not wear a spectacle frame. For the virtual fitting ofspectacle frames it is advantageous for the user not to wear a spectacleframe during recording.

The depth information detection unit can operate on the basis ofinfrared radiation. As a result, a user is not disturbed by themeasurement. An example may be a camera-based infrared depth sensor inwhich an infrared pattern is generated by a projection system and, bythe scene thus illuminated being recorded with an infrared camera, thedepth of the objects in the scene can be determined, that is to say thata depth profile of the head can be created, for example. Depth sensorsof this type are commercially available. They allow comparatively highframe rates, for example of 30 Hz or 60 Hz.

Patterns in the visible light range can also be used instead of infraredpatterns. Methods of this type are also known by the term stripeprojection. Here different image patterns and/or image sequences areprojected onto a surface (onto the head in this case) and an image ofthe object is recorded by a camera (which can be the 2D camera mentionedabove or can be different from the latter). In this case, the camera issituated at a defined angle with respect to the projection system. As aresult of the three-dimensional surface of the measurement object, hereof the head, and the triangulation baseline (that is to say distancebetween the projector and the camera), the patterns imaged on the imagesensor of the camera appear altered or deformed, from which the depthinformation and the topography of the illuminated surface can in turn bedetermined. In particular, the distance between the head and the depthinformation detection unit can thus also be determined. The use ofinfrared light as described above is preferred, however, since in thiscase a normal image recording is not disturbed and, for example, theuser is not put off by the light patterns either.

The depth information detection unit can comprise a time-of-flightsensor used to determine the distance by way of a time of flight of asignal, wherein the time of flight can be measured directly or in theform of a phase shift.

In the case of such time-of-flight sensors, essentially a signal is sentfrom the depth information detection unit to the head and a signalreflected from the head is detected. From the time of flight of thesignal to and from the head and the velocity of the signal it is thenpossible to determine the distance, wherein this can also be carried outat a multiplicity of points for example with a scanning method. Insteadof the time of flight being measured directly, often—particularly iflight pulses are used as a signal—a phase difference between amodulation of the reflected ray and a corresponding modulation of thereference ray derived from the transmitted ray is determined.

However, other types of signals, for example ultrasonic signals, canalso be used instead of light pulses.

According to an aspect of the invention, use is made of time-of-flightsensors which are used by so-called time-of-flight cameras havinglaterally resolving depth sensors. Examples of suitable sensors fortime-of-flight cameras of this type are photomixing detector sensors(PMD sensors; from the English term “Photonic Mixing Device”). Thesesensors use a modulated light signal, for example infrared light, toilluminate the head and detect the reflected light with the PMD sensor,which is likewise coupled to a modulation source used for themodulation. Here the time of flight is thus measured indirectly by wayof a phase shift.

With corresponding time-of-flight sensors it is possible here to scanobjects such as the head with a high frame rate of, for example, in therange of 30 to 60 Hz and high resolution, such that items of depthinformation can be made available with frame rates comparable to a videorate. In this case, an entire depth profile of the head can be created.

Time-of-flight sensors of this type thus make it possible to determinedepth information with a high frame rate and/or a high accuracy. Arobust detection of the depth information, largely independently of roomlighting, etc., can thus be realized as well, since e.g., it is notnecessary to find corresponding points in stereo image pairs.

Another type of depth information detection units which can be used inexemplary embodiments uses a distance measurement by means of opticaltriangulation, for example laser triangulation. The principle of opticaltriangulation is based on a light spot being generated on the object tobe measured (the head or a part thereof in the present case) with alaser, a light emitting diode (LED) or some other light source. This canbe done in the visible range or else in the infrared range. The lightspot is imaged via a camera, for example a CCD (charged coupled device)camera, a CMOS camera or a linear-array camera. The light source and thecamera are situated at a defined angle with respect to one another. Onaccount of the trigonometrical relationships, the distance to the objectto be measured can be determined from the displacement of the imagedlight spot on the sensor, that is to say the position of the light spoton the sensor. In particular, the light spot is displaced in the imagewith increasing distance to the object to be measured in a directionfrom the light source to the camera since, on account of the anglebetween light source and camera, with increasing distance the light alsocovers a greater path distance in the direction of the camera.

A measurement of this type can also be carried out line by line. Forthis purpose, by way of example, a laser line is projected onto thehead. From a camera image of the laser line, it is then possible tocommunicate the depth information along the laser line in particular onthe basis of displacements perpendicular to the direction of the laserline. It is thus possible to determine the topography of the head alongthe line. With a scanning system in which the laser line moves over thehead, the entire head or a part of interest thereof, for example an eyeportion including spectacles, can then be measured.

In this case, particularly with the use of a laser light source, careshould be taken to ensure that the eyes of the person to be examinedcannot be damaged by the laser. In particular, the intensity of thelaser should be chosen to be sufficiently low. Infrared light is typicalhere.

A camera for such an optical distance measurement by triangulation maybe a camera that is separate from a 2D camera that is additionallypresent, if appropriate, for the image recording. It is also possible touse a single camera unit, which, by way of example, with the use ofvisible light, can use regions outside the abovementioned laser line orother light lines for the image recording and can simultaneously recordthe laser line or, with the use of infrared light, can be switchableperiodically between the measurement of depth information and therecording of an image for example with a switchable filter. In otherexemplary embodiments, no image recording at all is carried out using a2D camera, rather only a scanning system as described above, forexample, in which a laser line is moved over the head, is used todetermine an entire depth profile and thus the topography of the head.

In a further exemplary embodiment, the depth information can also bedetermined by triangulation by a stereo camera method. In contrast toU.S. Pat. No. 7,740,355 B2 explained in the introduction, here a pair ofcameras is used not just for determining a 3D model, rather a distancebetween the head and the stereo cameras is explicitly determined aswell. Two cameras arranged at a predefined angle with respect to oneanother or a plurality of cameras arranged at a plurality of predefinedangles with respect to one another are used in this case.

With use of two cameras, such as a stereo camera system, the depthdetermination for an object point is carried out by way of adetermination of the parallax of the respective object point in the twocamera images, that is to say a displacement of object points betweenthe camera images. The error of such a depth measurement is proportionalto the square of the distance between the cameras and the head andinversely proportional to the stereo base, that is to say the distancebetween the two cameras. Consequently, here the stereo base must becomesufficiently large enough to achieve, for typical distances duringoperation of the device, a sufficient accuracy to obtain the depthinformation. In this case, “sufficient accuracy” means, in particular,that the parameters for spectacle fitting can be determined with anaccuracy that is desired or required for the spectacle fitting.

Since corresponding points or regions in the two image recordings haveto be identified in this procedure, that region of the head which is tobe examined has to have enough structure (in particular lines or edges)to be able to identify such a correspondence with a method used for thispurpose. Objects for which this usually proceeds well are eyes,eyebrows, nose and other distinctive facial features. In some exemplaryembodiments, moreover, another structure can be projected onto the head,for example binary patterns, lines, points, etc., to facilitate theidentification of corresponding regions.

In the case where the depth information detection unit is implementede.g., as a time-of-flight sensor or as a light field camera, a morecompact construction than with a stereo camera system, for example, ispossible, however, since no angle between two cameras need be provided.Consequently, time-of-flight sensors, light field cameras and the likeas depth information detection units, in cases in which a compactconstruction is of importance, are typical vis-à-vis a stereo camerasystem.

The present disclosure is not restricted to the types of depthinformation detection units described above. It is also possible to usedepth information detection units having other depth sensors, forexample—as already mentioned—ultrasonic depth sensors, depth sensorsthat carry out a depth measurement with optical coherence tomography(OCT), confocal sensors or chromatic confocal sensors. Overall it ispossible to use any conventional depth sensor which can detect depthinformation in relation to the head, in particular in relation to theeye portion and the spectacles, sufficiently accurately and at the sametime poses no danger to the user's eyes (for example owing toexcessively intensive radiation). “Sufficiently accurately” means onceagain that ultimately the parameters for spectacle fitting can bedetermined with an accuracy that is desired or required for spectaclefitting.

In addition to the depth information detection unit, the device furthercomprises a 2D camera as well, i.e., a (conventional) camera forrecording two-dimensional images with an image sensor, for recording animage of at least one part of the head. As a result, additionalinformation for determining the parameters for spectacle fitting isavailable, for example dimensions of the person's head that are takenfrom the image.

In this case, the evaluation unit can be configured for scaling theimages on the basis of the depth information and/or for scalingparameters for spectacle fitting, the parameters having been determinedon the basis of the images, on the basis of the depth information, asalready explained above.

The evaluation unit can additionally be configured for rectifying theimages on the basis of the depth information, as already explainedabove.

The device is configured in such a way that the depth informationdetection unit and the 2D camera detect the head via a common opticalaxis. In this case, in the case of the depth information detection unit,the optical axis corresponds to an axis on which the depth informationis detected, that is to say as it were to a “viewing direction” of thedepth information detection unit. If the depth information detectionunit uses an imaging optical unit, then the optical axis corresponds tothe optical axis of the imaging optical unit, usually a straight lineconnecting all centers of curvature of refractive or specularlyreflective surfaces of the imaging optical unit. Light rays on theoptical axis pass through the imaging optical unit without deflection.In the case of the 2D camera, the optical axis corresponds to theoptical axis of the lens of the 2D camera, in a manner corresponding tothe above explanation for an imaging optical unit.

In some exemplary embodiments, a beam splitter can be used for combiningand separating the optical axes of depth information detection unit and2D camera. The beam splitter can be a wavelength-selective beamsplitter. In exemplary embodiments of this type, by way of example, the2D camera can record visible light, while the depth informationdetection unit operates on the basis of infrared radiation. In otherexemplary embodiments, the beam splitter is not wavelength-selective,and the 2D camera and the depth information detection unit use at leastpartly an identical part of the spectrum. By virtue of such anarrangement, a more compact device than with a stereo camera or the likecan be achieved since no corresponding angle for example between imagerecording units need be provided. Moreover, depth information and imageinformation of the camera are recorded from the same direction, as aresult of which a perspective correction of the depth informationrelative to the image data can be obviated.

The evaluation unit can be configured to determine a head position ofthe head on the basis of the depth information, wherein determining theparameters for spectacle fitting is carried out on the basis of thedetermined head position.

The device can be configured to repeat a number of times the process ofdetecting the depth information with the depth information detectionunit and/or the process of recording the images using the 2D camera,wherein the evaluation unit is then configured for combining a pluralityof detected items of depth information and/or a plurality of recordedimages, e.g., in the form of an averaging as described above.

The evaluation unit can further be configured for rejecting imagesand/or items of depth information which satisfy predetermined criteria.

The evaluation unit can further be configured to represent a model ofthe head on the basis of the items of depth information e.g., on adisplay, and to enable virtual fitting of spectacles to the model,wherein the evaluation unit is configured to determine the parametersfor spectacle fitting on the basis of the virtual fitting.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will now be described with reference to the drawingswherein:

FIG. 1 shows a schematic illustration of a device in accordance with oneexemplary embodiment;

FIG. 2 shows a schematic illustration of a device in accordance with afurther exemplary embodiment;

FIG. 3 shows a schematic illustration of a device in accordance with afurther exemplary embodiment;

FIG. 4 shows a schematic illustration for elucidating depth sensors thatare able to be used in the exemplary embodiments;

FIG. 5 shows an illustration of a section through a depth profile suchas is able to be generated in some exemplary embodiments;

FIGS. 6A to 6F show illustrations for elucidating parameters forspectacle fitting;

FIG. 7 shows a flow diagram for elucidating a method in accordance withone exemplary embodiment;

FIG. 8 shows a flow diagram for elucidating a method in accordance witha further exemplary embodiment; and

FIGS. 9 and 10 show illustrations for elucidating a rectification suchas is carried out in some exemplary embodiments.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Various exemplary embodiments of the present disclosure are explained indetail below.

FIG. 1 schematically illustrates a device for determining parameters forfitting spectacles (i.e., parameters which can be used for fittingspectacles to a person's head) in accordance with one exemplaryembodiment. The device in FIG. 1 comprises a depth information detectionunit 12 for determining depth information with respect to a user's head10, in particular for determining depth information in relation to aneye portion, that is to say a region around the user's eyes, thereof. Inthis case, the user in FIG. 1 is wearing spectacles 11, with respect towhich depth information can likewise be determined.

In this case, depth information within the meaning of the presentapplication comprises at least one item of information in relation to adistance between the user, in particular the user's head 10 and/or thespectacles 11 worn by the user, and the depth information detection unit12. By way of example, the length of the dash-dotted line 14 in FIG. 1can be determined as the distance. It is possible however to measuredistances also with respect to other and/or a plurality of locations ofthe head 10. In one exemplary embodiment, a depth map, as it were, iscreated in this case, for example by determining the above-describeddistance for a multiplicity of points of the head 10, in particular ofthe eye portion, and/or a multiplicity of points of the spectacles 11.Information about such a distance is thus present as a result of thedepth information provided by the depth information detection unit 12.The information can be used hereinafter to determine parameters forfitting the spectacles 11 to the user's head 10, for example forcentration of spectacle lenses, independently of the exact position ofthe head 10. Examples of suitable depth information detection units andof parameters to be determined will be explained in even greater detaillater.

The device in FIG. 1 further comprises an evaluation unit 13, whichreceives the depth information from the depth information detection unit12 and determines parameters for fitting the spectacles 11 on the basisof the depth information. In this case, the evaluation unit 13 can beembodied for example as a correspondingly programmed computing unit, forexample in the form of a computer. However, it is also possible to usehardwired hardware components such as application-specific integratedcircuits (ASICs). In an inherently conventional manner, the evaluationunit 13 can comprise output means such as a display, loudspeakers,interfaces for outputting signals and the like to output the determinedparameters for spectacle fitting or to forward them to other units.Details of the determination of the parameters for spectacle fittingwill likewise be explained in even greater detail later.

It should be noted that the depth information detection unit 12 and theevaluation unit 13 of the device according to the disclosure can bearranged locally close together, for example in a common housing or elsein separate housings situated in a fixed spatial arrangement withrespect to one another. However, the evaluation unit 13 can likewisealso be arranged spatially separately from the depth informationdetection unit 12, and the depth information determined by the depthinformation detection unit 12 can be transmitted to the evaluation unit13 conventionally in a wireless manner, in a wired manner or else viaoptical lines such as optical fibers. A transmission of this type isalso possible for example via networks such as the Internet, such thatsubstantially arbitrary distances between the depth informationdetection unit 12 and the evaluation unit 13 are possible.

Before various details of depth information detection units, parametersfor spectacle fitting and the determination thereof are explained morespecifically, variations and extensions of the exemplary embodiment inFIG. 1 will now firstly be discussed with reference to FIGS. 2 and 3. toavoid repetition, in the following description identical or mutuallycorresponding elements in different FIGS. bear the same reference signsand are not repeatedly explained in detail.

In the case of the device in FIG. 2, the device from FIG. 1 is extendedby a camera 20, which records a two-dimensional image, for example ablack-and-white image or a color image, of the head 10 or of a partthereof, for example an eye portion. The camera 20 can be implemented ina conventional manner with a lens and an image sensor.

The image thus recorded is likewise fed to the evaluation unit 13. Inthis case, the evaluation unit 13 determines the parameters forspectacle fitting additionally on the basis of the recorded image. Inthis case, the evaluation unit 13 can additionally control the camera 20and the depth information detection unit 12 such that the image isrecorded simultaneously with the depth information.

For evaluation purposes, in one variant, by way of example, the imagerecorded by the camera 20 can then be scaled on the basis of the depthinformation detected by the depth information detection unit 12. By wayof example, a scaling of this type can be carried out with a higherscaling factor if the depth information indicates that the head 10 isfurther away from the depth information detection unit 12, and with asmaller scaling factor if the head is closer to the depth informationdetection unit 12. The scaling factor can indicate a magnification or areduction.

In this way, in particular, the image can be scaled such that dimensionsof the head 10 are able to be taken from the image sufficientlyaccurately, which dimensions can correspond to the parameters to bedetermined for spectacle fitting or on the basis of which dimensionssuch parameters for spectacle fitting are determinable. “Sufficientlyaccurately” means that ultimately the parameters for spectacle fittingare determinable with an accuracy that is desired or required forspectacle fitting. Instead of a scaling of the image, in anothervariant, corresponding dimensions can likewise also be taken from therecorded image, and the dimensions taken can then be scaled on the basisof the depth information.

In FIG. 2, the camera 20 is illustrated as separate from the depthinformation detection unit 12. In some exemplary embodiments, however,the camera 20 can also simultaneously serve as part of the depthinformation detection unit 12, for example in the case of stripeprojection or laser triangulation, as will be explained in greaterdetail later.

In the exemplary embodiment in FIG. 2, the camera 20 and the depthinformation detection unit 12 operate at different angles and withdifferent optical axes, as illustrated. In other exemplary embodiments,a construction is provided in which depth information detection unit 12and camera 20 view the head 10 coaxially. A corresponding exemplaryembodiment is illustrated in FIG. 3.

In FIG. 3, as in the exemplary embodiment in FIG. 2, a depth informationdetection unit 12 and a camera 20 are provided. In the exemplaryembodiment in FIG. 3, a beam splitter 30 is additionally provided, whichcombines the optical axis of the camera 20 with the optical axis 12 ofthe depth information detection unit 12, such that the head 10 is viewedor measured on a single optical axis. By this means, too, a compactconstruction is possible. Moreover, parallax errors and the like betweenthe depth information and the image recorded by the camera 20 areavoided or reduced. In the exemplary embodiment in FIG. 2, by contrast,such parallax errors and the like can be eliminated computationally bythe evaluation unit 13.

The beam splitter 30 can be a wavelength-selective beam splitter. Inexemplary embodiments of this type, by way of example, the camera 20 canrecord visible light, while the depth information detection unit 12operates on the basis of infrared radiation. Alternatively, the beamsplitter 30 is not wavelength-selective, and the camera 20 and the depthinformation detection unit 12 use at least partly an identical part ofthe spectrum.

Even though FIG. 3 does not explicitly illustrate this, here as well thedepth information provided by the depth information detection unit 12and one or a plurality of images provided by the camera 20 can beevaluated by an evaluation unit as explained for the evaluation unit 13from FIG. 1, to obtain parameters for spectacle fitting.

Next, various types of depth information detection units which can beused to obtain the depth information will be explained in greaterdetail.

By way of example, time-of-flight or phase angle measurements can beused for obtaining the depth information. In methods of this type, asexplained furtherabove, essentially a signal is sent from the depthinformation detection unit to the head and a signal reflected from thehead is detected. With corresponding time-of-flight sensors it ispossible here to scan objects such as the head 10 with a high frame rateof, for example, in the range of 30 to 60 Hz and high resolution, suchthat the depth information can be made available with frame ratescomparable to a video rate. In this case, an entire depth profile of thehead can be created. On the basis of such depth profiles, as in theexemplary embodiment in FIG. 1, parameters for spectacle fitting can bedetermined in principle even without the use of a further camera such asthe camera 20.

FIG. 4 schematically shows a depth information detection unit which canserve as a schematic illustration for various usable types of depthinformation detection units. In the case of a time-of-flight sensor, 40denotes a signal source, for example a modulated light source, and 41denotes a corresponding sensor for detecting the received light, forexample a time-of-flight camera as described above.

As likewise already explained, a further type of depth informationdetection units which can be used in exemplary embodiments uses adistance measurement by optical triangulation, for example lasertriangulation. In the case of FIG. 4, with a triangulation unit of thistype, for example, 40 may denote a light source and 41 a camera, whichare situated at a defined angle with respect to one another.

A further possibility for implementing the depth information detectionunit 12 is the use of a light field camera.

Further possibilities for implementing a depth information unit include,as described, a camera-based infrared depth sensor, in which an infraredpattern is generated by a projection system and, with the scene thusilluminated being recorded by an infrared camera, the depth of theobjects in the scene is determined. As likewise described, it is alsopossible to use stripe projection with visible light.

In the case of FIG. 4, here then for example the element 40 would be theprojection system, and the element 41 the camera, which can be identicalwith the camera 20 or different therefrom.

In a further exemplary embodiment, as described, the depth informationcan also be determined by triangulation by a stereo camera method. Inthis case, two or more cameras are arranged at one or a plurality ofpredefined angles. In the case of FIG. 4, with a depth informationdetection unit of this type, for example, 40 is a first camera and 41 isa second camera.

The use of such depth sensors as described above makes it possible, withcorresponding high-resolution depth sensors, to model a profile of thehead 10 and thus the three-dimensional surface of the head 10 based onthe depth information detection unit alone. As an example, FIG. 5 showsa schematic illustration of a section 50 through a 3D model of thistype, in which a section 51 through the spectacles is also visible. Thesection 50 in the example in FIG. 5 is placed through an eye 52 of theuser, that is to say does not extend through the center of the subject'sface, but rather through the center of the eye. 10 denotes the profileof the head as illustrated in FIGS. 1-4, wherein this profile extendsthrough the central axis of the head and thus differs from the profile50.

On the basis of the depth information, which includes a distance betweenthe depth information detection unit and the head 10, it is possible tocreate a true-to-size three-dimensional profile of this type of the head10, with corresponding sections 50 at the various locations. Parametersfor spectacle fitting such as centration parameters can in turn bedetermined therefrom. This is explained in greater detail below.

Firstly, variously determinable parameters for spectacle fitting, inparticular centration parameters, will be explained here with referenceto FIGS. 6A to 6F. FIGS. 6A to 6F here show in each case views ofspectacles, if appropriate together with a partial view of a head, toelucidate various parameters.

FIG. 6A shows the monocular pupillary distance when looking to infinity.An arrow 60A shows the monocular pupillary distance for a left eye,measured as the distance between the pupil and a central axis 61 of thehead. An arrow 60B shows the monocular pupillary distance for the righteye. The values for the left and right eyes are different in most cases.

FIG. 6B illustrates the fitting height, measured in turn when looking toinfinity, wherein the requirement of the fulcrum of the eye wassatisfied. The requirement of the fulcrum of the eye means that theoptical axis of the spectacle lens should extend through the fulcrum ofthe eye. In this case, the optical axis extends through the opticalmidpoint of the spectacle lens and is generally perpendicular to thespectacle lens. This can minimize undesired prismatic effects if eyemovements result in viewing through different parts of a spectacle lens.The fitting height indicates the distance between the pupil and a loweredge of the spectacle lens. An arrow 62A shows the fitting height forthe right eye, and an arrow 62B shows the fitting height for the lefteye.

In FIG. 6C, 63 denotes the corneal vertex distance, which is generallymeasured from the back side of the spectacle lens of the spectacles to avertex plane of the cornea of the eye. In FIG. 6D, an angle 64 denotesthe forward inclination of the frame, essentially an inclination of thespectacles with respect to the perpendicular. The inclination, like thefitting height shown in FIG. 6B, too, also depends on the person's headposture.

In FIG. 6E, an angle 65 denotes the frame disk angle, an angle at whichthe spectacle lens is situated compared with “planar” spectacles.Finally, FIG. 6F also indicates various dimensions of the spectacleframe itself 67 denotes the disk width, and 68 the disk height. Diskwidth and disk height together with pupillary distance and fittingheight are important items of information for determining a requiredlens diameter of a spectacle lens. 66 additionally denotes the bridgewidth of the spectacle frame.

FIGS. 6A to 6F show some parameters for spectacle fitting which can bedetermined with the devices illustrated. Further parameters forspectacle fitting can also be determined. By way of example, for thecentration of spectacle lenses for near vision (for example for readingspectacles or spectacles for work) and for the centration of progressivelenses there may be further parameters which can be determined. Theseinclude for example the “near pupillary distance”, which is not measuredwith viewing direction infinity as described above, but rather whenlooking at an object situated near and in front of the head.

Besides the parameters for spectacle fitting illustrated in FIG. 6F, itis also possible to determine other items of geometric information aboutthe spectacle frame. These items of geometric information may beimportant for the selection of suitable spectacle lenses since theyinfluence the lens thickness for example in the case of spectacle lenseshaving positive optical power.

The requirement of the fulcrum of the eye is generally satisfied atleast in the centration of single vision lenses. In the case of heightcentration, that is to say the alignment of the optical axis of thespectacle lens in the height direction, the head posture must be takeninto account here since the inclination of the head influences themeasurement of the fitting height and also the forward inclination ofthe frame. to take this into account, by way of example, in the case ofa measurement with the discussed device with the person's head postureit is possible to ensure that the plane of the spectacle frame isperpendicular to the ground, which is also referred to as the zeroviewing direction. In this state, the discussed device is then used todetermine the position of the pupils in the plane of the spectacle lens.It is likewise possible to determine the fitting height with naturalhead and body posture, wherein the person to be examined usually looksat the ground at 8 to 10 m, which is also referred to as the mainviewing direction. As will be explained in greater detail below, thehead posture can also be determined with the device according to thedisclosure, and the person to be examined can be instructed, ifappropriate, to change the head posture.

The procedures for determining centration parameters on the basis of thedepth information and, if appropriate, on the basis of a camera image(recorded for example by the camera 20 of the exemplary embodimentsabove) will now be explained in greater detail below with reference toFIGS. 7 to 10.

FIG. 7 shows a flow diagram that gives an overview of a method inaccordance with one exemplary embodiment for determining parameters forspectacle fitting. FIG. 8 then shows a detailed flow diagramillustrating various possible details of a method of this type. Whilethe methods are illustrated as a sequence of steps, the orderillustrated should not be interpreted as restrictive. In particular,some steps can also be carried out in a different order or one or moresteps can also be carried out in parallel. By way of example, depthinformation and an image can be recorded simultaneously by a depthinformation detection unit such as the depth information detection unit12 from FIG. 2 and a camera such as the camera 20 from FIG. 2 or else bya light field camera as explained above.

A step 70 in FIG. 7 involves detecting depth information comprising adistance between a head and a unit used for detecting the depthinformation. This can be done using depth information detection units 12as discussed above.

Step 71 involves additionally capturing an image (also referred to asoverview image) of at least one region of interest, for example an eyeportion, of a head. Step 71 is optional, and, in some exemplaryembodiments, only the depth information is detected in step 70.Parameters serving for spectacle fitting, in particular spectacle lenscentration, are then determined in step 72. By way of example, one ormore of the parameters discussed with reference to FIGS. 6A to 6F can bedetermined.

For this purpose, in some exemplary embodiments, a true-to-size 3D modelof the head with spectacles is created from the detected depthinformation, and the parameters are then read off from this 3D model. Inaddition, if an overview image was captured, the overview image can beregistered to the 3D model, for example be used to give texture to the3D model. This facilitates the recognition of individual features suchas the eyes, for example. Procedures for recognizing features of thistype such as the eyes, the spectacle frame and the like, which arerequired for determining the parameters, are inherently known forexample from conventional photography, where various face recognitionalgorithms are used. The distance between the head and the depthinformation detection unit can be used here to ensure a correct size ofthe 3D model even in the case of a positioning of the head that does notcorrespond to a predefined setpoint position.

In other exemplary embodiments, the depth information can even comprisejust a single distance between the head and the device at a singlepoint, and an overview image is additionally recorded. Depth informationof this type can be provided by a relatively simple depth sensor which,for example, need not be embodied in scanning fashion. In this case, thedistance thus determined is used to scale the image with a scalingfactor, which is dependent on the distance and which essentially resultsdirectly from the intercept theorem. In this regard, the recorded imagecan be scaled to a correct size, and dimensions such as the dimensionsillustrated in FIGS. 6A to 6F can be taken from the overview image thusscaled. In this case, depending on the recording direction for anindividual image only some parameters need be determined. By way ofexample, parameters in FIGS. 6A, 6B and 6F can be determined from afrontal recording, while an image from the side has to be produced forthe parameters in FIGS. 6C and 6D. Depending on parameters to bedetermined, therefore, if appropriate a plurality of image recordingsare carried out in such a case.

In some exemplary embodiments, therefore, the depth informationcompensates for the fact that the size of the head of the person to beexamined or of relevant parts thereof changes depending on a distancebetween the head and the camera used. By way of example, the headappears larger if it is situated closer to the camera, and smaller if itis situated at a distance from the camera.

Various details and extensions of the method from FIG. 7 will now bediscussed with reference to FIG. 8. While FIG. 8 and the followingdescription explain various possible extensions and details incombination, it should be noted that these can also be realizedindependently of one another, that is to say need not necessarily beimplemented in combination with one another.

Step 80 involves repeatedly detecting depth information, and,optionally, step 81 involves repeatedly recording image information.Steps 70 and 71 from FIG. 7 are thus carried out repeatedly. As alreadyexplained, some depth sensors offer high frame rates in the region of 30Hz or 60 Hz, that is to say in the region of typical video rates, andcameras can also record image information at such rates. However, lowerframe rates are also possible. These measurements in 80 and 81 can beanalyzed in real time at least in relation to some aspects byappropriately equipped computers.

As already explained, from items of depth information repeatedlydetected in this way, a model of the head can then be created anddisplayed on a display, which enables for example fitting of a virtualspectacle frame as described. Moreover, the items of depth informationcan be used for aligning the head, as described.

In step 82, suitable measurements can then be selected from themeasurements carried out in 80 and 81. In this regard, disadvantageousimages or items of depth information can be excluded for the laterdetermination of the parameters for spectacle fitting. By way ofexample, the position of the pupil, which is required for example forthe parameters illustrated in FIGS. 6A and 6B, can be determined onlyinaccurately with the eyelid closed. Therefore, with correspondingdetection of facial features (also referred to as Facial FeatureDetection or Landmark Detection in the literature in English) it ispossible to determine in which images or in which items of depthinformation one or both eyelids are closed, and corresponding data canbe rejected for the subsequent processing steps. It should be noted herethat detecting the items of depth information and recording the imagesin 80 and 81 can also be carried out in a synchronized manner, such thata set of depth information is assigned for example to a respectiveimage. If it is ascertained for example in the image that the eyelid isclosed, the associated depth information can also immediately berejected. Conversely, if it is ascertained for example in the depthinformation that the head was turned to an extent such that a reasonabledetermination of desired parameters for spectacle fitting is possibleonly with difficulty or is not possible, the corresponding image canalso be rejected.

Next, a combination of a plurality of measurements and/or a registrationof data to one another can be carried out in step 83. In this case,registration is generally understood to mean a process in which aplurality of data sets is brought to congruence or aligned with oneanother. In so-called rigid registration methods, in this case thetopography of the individual measurements is not altered, i.e.,distances and angles are maintained, rather the individual measurementsare brought to congruence with one another only by rotation andtranslation.

In this way, a plurality of measurements carried out in succession (insteps 80 and 81 in FIG. 8) can be combined after registration, which canbring an improvement in accuracy in particular in relation to the itemsof depth information. The parameters for the registration can bedetermined by conventional optimization methods, for example the ICP(Iterative Closest Point) algorithm for data without a texture,homographic estimation, for example with a DLT algorithm for image data(direct linear transformation; for example, for image data recorded by acamera).

However, such rigid registration methods for combination can beproblematic in the case of variable facial regions (for example movingeyelids) since a disadvantageous registration in particular forrepresentation purposes on a display or the like can take place here. Inexemplary embodiments, therefore, for such image regions or regions ofthe items of depth information in which rapid changes can typicallyoccur (in particular eyelid, eye movements and the like), non-rigidmethods are used.

Step 84 then involves determining a head posture in the measurementsfrom steps 80 and 81. The head posture can then be used to rectifyrecorded images, or else be used for correction for example in someother way during the determination of the parameters for spectaclefitting.

In one exemplary embodiment, in this case, with registration methodssuch as those explained above in relation to step 83, the head of therecorded person is registered with a standard head (that is to say a 3Dmodel of a head of a shape defined as standard) and the posture of thestandard head is determined with respect to a reference coordinatesystem of the device. The reference coordinate system is also determinedas a world coordinate system. For this purpose, one exemplary embodimentinvolves determining the rigid transformation which transforms thestandard head given in its own reference system into a standard head inthe world coordinate system, such that the best possible correspondenceto the measurement data of the depth information detection unit isachieved. This transformation can be described for example with the aidof the following six parameters: translation in x-, y- and z-directions,and rotation about x-, y- and z-axes (for example according to Euler'sformula), wherein x, y and z describe axes of a world coordinate system.

As an example, FIG. 9 illustrates a head 10 that is rotated by an angle90 about the z-axis (perpendicular to the image plane). 91 denotes thecentral axis of a head aligned straight, and 92 denotes the central axisof the head 10. Here the angle 90 would thus be determined by theregistration. Translations or rotations of the head 10 about the x-and/or y-axis can also be determined in a corresponding manner.

The head posture thus described with these six parameters is then usedin step 85, described below, to correct a possible oblique position ofthe viewing direction toward the device. In this way, it is possible forexample to correct a viewing point, that is to say the intersectionpoint of the person's respective visual axis with a plane of thespectacle lens.

One possibility for applying a correction in advance is therectification of the camera image (for example of the images recorded instep 81) in step 84 to convert the camera images to an image planecorresponding to an alignment of the face. This is explained withreference to FIG. 10. In FIG. 10, the head 10 is once again illustratedin the position in FIG. 9. 100 shows an optical center of a camera used(for example the camera 20 of the exemplary embodiments describedabove). 101 denotes an image plane of the central projection from thecenter 100, for example an image plane according to which the image isrecorded by the camera 20. The oblique position of the head 10 resultshere in distortions for example between the left and right halves of theface. During the rectification, the points of the image plane 101 areconverted into an image plane 102 substantially in accordance with thelight rays depicted, which results in the correction, and the image thuscorrected is fitted to the alignment of the face since the image plane102 corresponds to the alignment better than the image plane 101.Parameters for spectacle fitting can then be taken from such correctedimages (which if appropriate have been scaled as discussed above).

In step 85, as already indicated above, an analysis of the items ofdepth information and/or images which were preprocessed in steps 82 to84 is then carried out to determine the parameters for spectaclefitting. As already explained, this can be carried out essentially usingalgorithms for detecting facial features or other features (for exampleof the spectacle frame), and corresponding parameters for spectaclefitting can then be implemented with corresponding distance or anglemeasurements in the data, for example in a 3D model created on the basisof the items of depth information and/or in image data scaled and/orrectified on the basis of the items of depth information. In this way,the parameters for spectacle fitting, in particular the centrationparameters, can be determined in a simple manner.

As already explained, in some exemplary embodiments, it is also possiblefor only some of the steps elucidated in FIG. 8 to be carried out. Byway of example, steps 83 and 84 can also be carried out independently ofone another, and also be carried out if only one measurement of depthinformation is carried out, or only one measurement of depth informationand one recording of an image. In other words, the multiple imagerecording and averaging can also be omitted.

Further, the current disclosure comprises exemplary embodimentsaccording to the following clauses:

Clause 1. A method for determining parameters for spectacle fitting,comprising:

detecting depth information in relation to a user's head with a depthinformation detection unit, the depth information comprising a distancebetween the user's head and a device used for the detecting andcomprising the depth information detection unit, anddetermining parameters for spectacle fitting on the basis of the depthinformation, recording a 2D image of the head with a 2D camera,wherein recording the 2D image and detecting the depth information arecarried out via a common optical axis, wherein the 2D camera isdifferent than the depth information detection unit.

Clause 2. A method for determining parameters for spectacle fitting,comprising:

detecting depth information in relation to a user's head with a depthinformation detection unit, determining parameters for spectacle fittingon the basis of the depth information, recording a 2D image of the headwith a 2D camera,

-   -   i) wherein recording the 2D image and detecting the depth        information are carried out via a common optical axis, wherein        the 2D camera is different than the depth information detection        unit.

Clause 3. The method according to clause 1 or 2, wherein the methodfurther comprises determining a head position of the head, whereindetermining the parameters for spectacle fitting is carried out on thebasis of the determined head position.

Clause 4. The method according to any of clauses 1 to 3, whereindetermining the parameters for spectacle fitting is carried out on thebasis of the recorded 2D image.

Clause 5. The method according to clause 4, comprising scaling the 2Dimage on the basis of the depth information and/or scaling parametersfor spectacle fitting, the parameters having been determined on thebasis of the 2D image, on the basis of the depth information.

Clause 6. The method according to clause 4 or 5, further comprisingrectifying the 2D image on the basis of the depth information.

Clause 7. The method according to any of clauses 1 to 6, whereindetecting the depth information and/or recording the 2D image are/isrepeated a number of times, wherein the method further comprisesaveraging over a plurality of detected items of depth information and/orover a plurality of recorded images.

Clause 8. The method according to clause 7, further comprising rejecting2D images and/or items of depth information which satisfy predeterminedcriteria.

Clause 9. The method according to any of clauses 1 to 8, furthercomprising:

-   -   i) representing a model of the head on the basis of the depth        information, and    -   ii) virtually fitting spectacles to the model,    -   iii) wherein the parameters for spectacle fitting are determined        on the basis of the virtual fitting.

Clause 10. A method for determining parameters for spectacle fitting,comprising:

detecting depth information in relation to a user's head, the depthinformation comprising a distance between the user's head and a deviceused for the detecting, and

determining parameters for spectacle fitting on the basis of the depthinformation,

recording a 2D image of the head,

wherein recording the 2D image and detecting the depth information arecarried out via a common optical axis, and

wherein detecting the depth information and/or recording the 2D imageare/is repeated a number of times, wherein the method further comprisesaveraging over a plurality of detected items of depth information and/orover a plurality of recorded images.

Clause 11. A method for determining parameters for spectacle fitting,comprising:

detecting depth information in relation to a user's head,

determining parameters for spectacle fitting on the basis of the depthinformation,

recording a 2D image of the head,

wherein recording the 2D image and detecting the depth information arecarried out via a common optical axis, and

wherein detecting the depth information and/or recording the 2D imageare/is repeated a number of times, wherein the method further comprisesaveraging over a plurality of detected items of depth information and/orover a plurality of recorded images.

Clause 12. The method according to any of the preceding clauses, furthercomprising: combining optical axes of the depth information detectionunit and the 2D camera to form the common optical axis with a beamsplitter.

Clause 13. A device for determining parameters for spectacle fitting,comprising:

-   -   i) a depth information detection unit for detecting depth        information with respect to a user's head, the depth information        comprising at least one distance between the head and the        device,    -   ii) an evaluation unit configured to determine the parameters        for spectacle fitting on the basis of the detected depth        information, and    -   iii) a 2D camera for recording an image of at least one part of        the head,    -   iv) wherein the device is configured in such a way that the        depth information detection unit and the 2D camera detect the        head via a common optical axis.

Clause 14. A device for determining parameters for spectacle fitting,comprising:

-   -   i) a depth information detection unit for detecting depth        information with respect to a user's head,    -   ii) an evaluation unit configured to determine the parameters        for spectacle fitting on the basis of the detected depth        information, and    -   iii) a 2D camera for recording an image of at least one part of        the head,    -   iv) wherein the device is configured in such a way that the        depth information detection unit and the 2D camera detect the        head via a common optical axis.

Clause 15. The device according to clause 13 or 14, wherein the 2Dcamera is different from the depth information detection unit.

Clause 16. The device according to any of clauses 13 to 15, wherein thedepth information detection unit comprises a light field camera.

Clause 17. The device according to any of clauses 13 to 16, wherein thedepth information detection unit operates on the basis of infraredradiation.

Clause 18. The device according to any of clauses 13 to 17, wherein thedepth information detection unit is configured to detect a depth profileof a region of interest of the head, and wherein the evaluation unit isconfigured to display a three-dimensional model of the region ofinterest.

Clause 19. The device according to any of clauses 13 to 18, wherein thedepth information detection unit comprises a unit based ontime-of-flight measurements and/or phase measurements and/ortriangulation and/or pattern projection and/or stereo image recording.

Clause 20. The device according to any of clauses 13-19, wherein thedevice comprises a beam splitter, wherein the beam splitter is arrangedto combine optical axes of the depth information detection unit and the2D camera to form the common optical axis.

Clause 21. The device according to clause 20, wherein the beam splitteris a wavelength-selective beam splitter arranged to forward visiblelight to the 2D camera and infrared light to the depth informationdetection unit.

Clause 22. A method for determining parameters for spectacle fitting,comprising:

detecting depth information in relation to a user's head with a depthinformation detection unit, the depth information comprising a distancebetween the user's head and a device used for the detecting andcomprising the depth information detection unit, anddetermining parameters for spectacle fitting on the basis of the depthinformation, and

-   -   i) representing a model of the head on the basis of the depth        information, and    -   ii) virtually fitting spectacles to the model,        wherein the parameters for spectacle fitting are determined on        the basis of the virtual fitting, recording a 2D image of the        head with a 2D camera,        wherein recording the 2D image and detecting the depth        information are carried out via a common optical axis, wherein        the 2D camera is different than the depth information detection        unit.

Clause 23. A method for determining parameters for spectacle fitting,comprising:

detecting depth information in relation to a user's head by means of adepth information detection unit,

determining parameters for spectacle fitting on the basis of the depthinformation, and

-   -   i) representing a model of the head on the basis of the depth        information, and    -   ii) virtually fitting spectacles to the model,        wherein the parameters for spectacle fitting are determined on        the basis of the virtual fitting, recording a 2D image of the        head by means of a 2D camera,        wherein recording the 2D image and detecting the depth        information are carried out via a common optical axis, wherein        the 2D camera is different than the depth information detection        unit.

Clause 24. The method according to clause 22 or 23, wherein the methodfurther comprises determining a head position of the head, whereindetermining the parameters for spectacle fitting is carried out on thebasis of the determined head position.

Clause 25. The method according to any of clauses 22 to 24, furthercomprising recording an image of the head, wherein determining theparameters for spectacle fitting is carried out on the basis of therecorded image.

Clause 26. The method according to clause 25, comprising scaling theimage on the basis of the depth information and/or scaling parametersfor spectacle fitting, the parameters having been determined on thebasis of the image, on the basis of the depth information.

Clause 27. The method according to clause 25 or 26, further comprisingrectifying the image on the basis of the depth information.

Clause 28. The method according to any of clauses 22 to 27, whereindetecting the depth information and/or recording the image are/isrepeated a number of times, wherein the method further comprisesaveraging over a plurality of detected items of depth information and/orover a plurality of recorded images.

Clause 29. The method according to clause 28, further comprisingrejecting images and/or items of depth information which satisfypredetermined criteria.

Clause 30. A method for determining parameters for spectacle fitting,comprising:

detecting depth information in relation to a user's head, the depthinformation comprising a distance between the user's head and a deviceused for the detecting, and

determining parameters for spectacle fitting on the basis of the depthinformation,

-   -   i) representing a model of the head on the basis of the depth        information, and    -   ii) virtually fitting spectacles to the model, wherein the        parameters for spectacle fitting are determined on the basis of        the virtual fitting,        recording a 2D image of the head,        wherein recording the 2D image and detecting the depth        information are carried out via a common optical axis, and        wherein detecting the depth information and/or recording an        image are/is repeated a number of times, wherein the method        further comprises averaging over a plurality of detected items        of depth information and/or over a plurality of recorded images.

Clause 31. A method for determining parameters for spectacle fitting,comprising:

detecting depth information in relation to a user's head,

determining parameters for spectacle fitting on the basis of the depthinformation,

-   -   i) representing a model of the head on the basis of the depth        information, and    -   ii) virtually fitting spectacles to the model, wherein the        parameters for spectacle fitting are determined on the basis of        the virtual fitting, recording a 2D image of the head,        wherein recording the 2D image and detecting the depth        information are carried out via a common optical axis, and        wherein detecting the depth information and/or recording an        image are/is repeated a number of times, wherein the method        further comprises averaging over a plurality of detected items        of depth information and/or over a plurality of recorded images.

Clause 32. The method according to any of clauses 22 to 31, furthermorecomprising: combining optical axes of the depth information detectionunit and the 2D camera to form the common optical axis by means of abeam splitter.

Clause 33. The method according to clause 32 or 12, wherein the beamsplitter is a wavelength-selective beam splitter arranged to forwardvisible light to the 2D camera and infrared light to the depthinformation detection unit.

Clause 34. A method for determining parameters for spectacle fitting,comprising:

detecting depth information in relation to a user's head by means of adepth information detection unit, and

determining parameters for spectacle fitting on the basis of the depthinformation,

characterized in that the depth information detection unit is selectedfrom the group consisting of a light field camera, a time-of-flightsensor and a camera-based infrared depth sensor, in which an infraredpattern is generated by a projection system and, by means of the scenethus illuminated being recorded by an infrared camera, the depth of theobjects in the scene is averaged, or in that the depth informationdetection unit operates on the basis of infrared radiation or on thebasis of patterns in the visible light range, or in that the depthinformation detection unit uses a distance measurement by means ofoptical triangulation.

Clause 35. A device for determining parameters for spectacle fitting,comprising:

a depth information detection unit for detecting depth information withrespect to a user's head, and

an evaluation unit configured to determine the parameters for spectaclefitting on the basis of the detected depth information,

characterized in that the depth information detection unit is selectedfrom the group consisting of a light field camera, a time-of-flightsensor and a camera-based infrared depth sensor, in which an infraredpattern is generated by a projection system and, by means of the scenethus illuminated being recorded by an infrared camera, the depth of theobjects in the scene is averaged, or in that the depth informationdetection unit operates on the basis of infrared radiation or on thebasis of patterns in the visible light range, or in that the depthinformation detection unit uses a distance measurement by opticaltriangulation.

The foregoing description of the exemplary embodiments of the disclosureillustrates and describes the present invention. Additionally, thedisclosure shows and describes only the exemplary embodiments but, asmentioned above, it is to be understood that the disclosure is capableof use in various other combinations, modifications, and environmentsand is capable of changes or modifications within the scope of theconcept as expressed herein, commensurate with the above teachingsand/or the skill or knowledge of the relevant art.

The term “comprising” (and its grammatical variations) as used herein isused in the inclusive sense of “having” or “including” and not in theexclusive sense of “consisting only of” The terms “a” and “the” as usedherein are understood to encompass the plural as well as the singular.

All publications, patents and patent applications cited in thisspecification are herein incorporated by reference, and for any and allpurposes, as if each individual publication, patent or patentapplication were specifically and individually indicated to beincorporated by reference. In the case of inconsistencies, the presentdisclosure will prevail.

LIST OF REFERENCE SIGNS

-   10 Head-   11 Spectacles-   12 Depth information detection unit-   13 Evaluation unit-   20 Camera-   30 Beam splitter-   40 Component-   41 Component-   50 Depth profile-   51 Spectacles-   52 Eye-   10 Head profile-   60A, 60B Pupillary distance-   61 Central line-   62A, 62B Fitting height-   63 Corneal vertex distance-   64 Forward inclination-   65 Frame disk angle-   66 Bridge width-   67 Disk width-   68 Disk height-   70-72; 80-85 Method steps-   90 Angle-   91 Central axis-   92 Central axis-   100 Optical camera center-   101 Image plane-   102 Rectified image plane

The invention claimed is:
 1. A method for determining parameters forspectacle fitting, the method comprising: detecting depth information inrelation to a user's head with a depth information detection unit,determining parameters for spectacle fitting based on the depthinformation, recording a 2D image of the user's head with a 2D camera,wherein the 2D camera and the depth information detection unit each havea respective optical axis, wherein the optical axis of the 2D imagecamera and the optical axis of the depth information detection unit arecombined, and wherein the 2D camera is different from the depthinformation detection unit, and rectifying the 2D image based on thedepth information by performing at least one of aligning or correctingthe 2D image to remove distortions in the 2D image.
 2. The method asclaimed in claim 1, further comprising: determining a head position ofthe user's head, wherein determining the parameters for spectaclefitting is carried out on based on the determined head position.
 3. Themethod as claimed in claim 1, further comprising: representing a modelof the user's head that has been obtained based on the depthinformation, and virtually fitting spectacles to the model, wherein theparameters for spectacle fitting are determined based on the virtualfitting.
 4. The method as claimed in claim 1, further comprising:determining the parameters for spectacle fitting based on the recorded2D image.
 5. The method as claimed in claim 4, further comprising:scaling at least one of the 2D image or the parameters for spectaclefitting based on the depth information, wherein the parameters forspectacle fitting have been determined based on the 2D image.
 6. Themethod as claimed in claim 1, wherein at least one of detecting thedepth information or recording the 2D image is repeated a number oftimes, and wherein the method further comprises: averaging over at leastone of a plurality of detected items of depth information or a pluralityof recorded images.
 7. The method as claimed in claim 6, furthercomprising rejecting at least one of a subset of 2D images from theplurality of recorded images or a subset of detected items of depthinformation from the plurality of detected items, which satisfypredetermined criteria.
 8. The method as claimed in claim 1, furthercomprising: combining the respective optical axes of the depthinformation detection unit and the 2D camera to form a common beam pathsegment with a beam splitter.
 9. The method as claimed in claim 8,wherein the beam splitter is a wavelength-selective beam splitterarranged to forward visible light to the 2D camera and infrared light tothe depth information detection unit.
 10. A method for determiningparameters for spectacle fitting, the method comprising: detecting depthinformation in relation to a user's head with a depth informationdetection unit, determining parameters for spectacle fitting based onthe depth information, recording a 2D image of the user's head with a 2Dcamera, wherein the 2D camera and the depth information detection uniteach have a respective optical axis, wherein the optical axis of the 2Dimage camera and the optical axis of the depth information detectionunit are combined, and wherein the 2D camera is different from the depthinformation detection unit, wherein at least one of detecting the depthinformation or recording the 2D image is repeated a number of times torecord a plurality of recorded images or a plurality of detected items,and rejecting at least one of a subset of 2D images from a plurality ofrecorded images or a subset of detected items of depth information fromthe plurality of detected items, which satisfy predetermined criteria.11. The method as claimed in claim 10, further comprising: determining ahead position of the user's head, wherein determining the parameters forspectacle fitting is carried out on based on the determined headposition.
 12. The method as claimed in claim 10, further comprising:determining the parameters for spectacle fitting based on the recorded2D image.
 13. The method as claimed in claim 10, further comprising:scaling at least one of the 2D image or the parameters for spectaclefitting based on the depth information, wherein the parameters forspectacle fitting have been determined based on the 2D image.
 14. Themethod as claimed in claim 10, wherein at least one of detecting thedepth information or recording the 2D image is repeated a number oftimes, and wherein the method further comprises: averaging over at leastone of a plurality of detected items of depth information or a pluralityof recorded images.
 15. The method as claimed in claim 10, furthercomprising: representing a model of the user's head that has beenobtained based on the depth information, and virtually fittingspectacles to the model, wherein the parameters for spectacle fittingare determined based on the virtual fitting.
 16. The method as claimedin claim 10, further comprising: combining the respective optical axesof the depth information detection unit and the 2D camera to form acommon beam path segment with a beam splitter.
 17. The method as claimedin claim 16, wherein the beam splitter is a wavelength-selective beamsplitter arranged to forward visible light to the 2D camera and infraredlight to the depth information detection unit.